The present invention relates to a naphthol derivative (to be also referred to as a xe2x80x9c1-naphthol compoundxe2x80x9d hereinafter) which functions as a precursor of a compound having an acidic proton, and a method for preparing a compound having an acidic proton. More specifically, the present invention relates to a compound which is stable under alkali hydrolysis conditions and can rapidly release a compound having an acidic proton or the dissociated form of the compound when a nucleophilic substituent is introduced to the 4-position of naphthol, and a method for preparing a compound having an acidic proton.
A 1-naphthol compound of the present invention can be used as a compound for releasing a photographically useful compound and the like in a silver halide photosensitive material.
A technique which converts a compound having an acidic proton into a nonprotic compound (to be referred to as a block body hereinafter) for a certain predetermined period and regenerates the compound from this block body by giving a certain type of stimulus at a desired timing, is used in various fields handling organic compounds. The best known is the concept of protection and deprotection in organic synthetic reactions. For example, when a certain type of conversion reaction is to be performed for a compound having an acidic proton, if the desired reaction does not well progress because the acidic proton exists, this portion is once protected by a protective group to perform the desired reaction, and finally deprotection is performed to regenerate the acidic portion. Also, in the field of silver halide photosensitive materials, a technique is known by which the block body of a photographically useful compound having an acidic proton is incorporated in a photographically inert form into a sensitive material and the photographically useful group is released during development (in some cases, only at a portion where the development progresses). Examples are development inhibitor-releasing couplers described in U.S. patent application Ser. No. 4,248,962 and Jpn. Pat. Appln. KOKAI Publication No. 5-313322 and bleaching accelerator-releasing couplers described in Jpn. Pat. Appln. KOKAI Publication No. 61-201247. This technique also has an important meaning as one method of a drug delivery system in the field of medical treatments.
The most generally known block body of a compound having an acidic proton is a compound protected by a carbonyl group, such as Axe2x80x94COR (A represents the moiety of a compound having an acidic proton the pKa of a corresponding protonated form (AH) of which is 0 to 14, and R represents, e.g., an alkyl group, aryl group, alkoxy group, or amino group). In this block body simply protected by a carbonyl group, the AH can be regenerated (deblocked) by hydrolysis under alkaline conditions. However, the stability as a block body and the ease of deblocking have a tradeoff relationship. That is, when the stability as a block body (Axe2x80x94COR) is raised, the deblocking conditions become strict. If the deblocking conditions become strict, it is well possible that the regenerated AH is further hydrolyzed under the deblocking conditions. If this is the case, Axe2x80x94COR cannot substantially be the block body of AH.
As a method of breaking the tradeoff relationship between the stability of the block body of a compound having an acidic proton and the ease of deblocking from this block body, blocking in the form of methoxymethyl ether or benzyl ether is known refer, for example, to PROTECTIVE GROUP IN ORGANIC SYNTHESIS, John Wiley and Sons, Inc., Second Edition pp. 149-150 and 156-158). While these block bodies are stable under alkaline conditions, methoxymethyl ether can be deblocked under relatively moderate acidic conditions. Also, benzyl ether can be readily deblocked under moderate catalitic reducing conditions. However, these block bodies cannot be used for compounds that are unstable under acidic or reducing conditions.
Furthermore, although the development inhibitor-releasing couplers and bleaching accelerator-releasing couplers in the field of silver halide photosensitive materials described above are relatively stable under alkali hydrolysis conditions, they can release development inhibitors and bleaching accelerates only at exposed portions during development. However, in these examples the synthesis of a block body and the ease of deblocking largely depend upon the type of body to be blocked. Also, an azomethine dye is generated in addition to deblocking. Hence, any of these examples is not highly versatile as the block body of a compound having an acidic proton.
It is an object of the present invention to provide a compound effective as the block body of a compound having an acidic proton, which is stable under alkali hydrolysis conditions and can rapidly regenerate a compound having an acidic proton or the dissociated form thereof when a nucleophilic group is introduced to a specific position in a molecule.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
The object of the present invention is achieved by a compound represented by formula (I) below: 
wherein A represents the moiety of a compound having an acidic proton the pKa of a corresponding protonated form (AH) of which is 0 to 14, R1 represents an aliphatic group, aryl group, or heterocyclic group, R2 represents a substituent, n represents an integer of 0 to 5, X represents a hydrogen atom, halogen atom, R11xe2x80x94, R11Oxe2x80x94, R11Sxe2x80x94, R11OCOOxe2x80x94, R12COOxe2x80x94, R12(R13)NCOOxe2x80x94, R12CON(R13)xe2x80x94, xe2x80x94NO, xe2x80x94NO2, or xe2x80x94Nxe2x95x90Nxe2x80x94R11, and Y represents an oxygen atom or sulfur atom. R11 represents an aliphatic group, aryl group, or heterocyclic group, and each of R12 and R13 independently represents a hydrogen atom, aliphatic group, aryl group, or heterocyclic group.
The present invention also provides a method for preparing a compound having an acidic proton in which a nucleophilic group is introduced to the 4-position of a 1-naphthol compound represented by formula (I) above and which is represented by AH by the intramolecular nucleophilic reaction.
Details of a compound represented by formula (I) will be described below.
A represents the moiety of a compound having an acidic proton the pKa of a corresponding protonated form (AH) of which is 0 to 14. Preferably, A represents the moiety of a compound having an acidic proton the pKa of a corresponding protonated form (AH) of which is 2 to 11.
Preferable examples of A are a 6- to 32-carbon, preferably 6- to 22-carbon substituted or nonsubstituted aryloxy group (e.g., phenoxy and naphthyloxy), a 1- to 32-carbon, preferably 1- to 22-carbon substituted or nonsubstituted heterocyclic oxy group (e.g., pyridyloxy and quinolyloxy), a 1- to 32-carbon, preferably 1- to 22-carbon substituted or nonsubstituted alkylthio group (e.g., methylthio, ethylthio, and butylthio), a 6- to 32-carbon, preferably 6- to 22-carbon substituted or nonsubstituted arylthio group (e.g., phenylthio and naphthylthio), a 1- to 32-carbon, preferably 1- to 22-carbon substituted or nonsubstituted heterocyclic thio group (e.g., tetrazolylthio, triazolylthio, oxazolylthio, imidazolylthio, benzimidazolylthio, benzothiazolylthio, and benzoxazolylthio), a 1- to 32-carbon, preferably 1- to 22-carbon substituted or nonsubstituted azole group (e.g., tetrazole, 1,2,3-triazole, 1,2,4-triazole, and benzotriazole), and a 2- to 32-carbon, preferably 2- to 22-carbon substituted or nonsubstituted carbonyloxy group (e.g., acetyloxy and benzoyloxy).
More preferable examples of A are an aryloxy group, heterocyclic oxy group, alkylthio group, arylthio group, heterocyclic thio group, and azole group described above (practical examples of these groups are those enumerated above).
R1 represents an aliphatic group (an aliphatic group means a saturated or unsaturated, chainlike or cyclic, straight-chain or branched, substituted or nonsubstituted aliphatic hydrocarbon group, and has the same meaning in the rest of the document), aryl group, or heterocyclic group.
An aliphatic group represented by R1 is an aliphatic group having preferably 1 to 32, and more preferably, 1 to 22 carbon atoms. Practical examples are methyl, ethyl, vinyl, ethynyl, propyl, isopropyl, 2-propenyl, 2-propynyl, butyl, isobutyl, t-butyl, t-amyl, hexyl, cyclohexyl, 2-ethylhexyl, octyl, 1,1,3,3-tetramethylbutyl, decyl, dodecyl, hexadecyl, and octadecyl. An aryl group represented by R1 is a substituted or nonsubstituted aryl group having preferably 6 to 32, and more preferably, 6 to 22 carbon atoms. Practical examples are phenyl, tolyl, and naphthyl. A heterocyclic group represented by R1 is a substituted or nonsubstituted 3- to 8-membered, preferably 5- or 6-membered heterocyclic group having preferably 1 to 32, and more preferably, 1 to 22 carbon atoms. Practical examples are 2-furyl, 2-pyrolyl, 2-thienyl, 3-tetrahydrofuranyl, 4-pyridyl, 2-pyrimidinyl 2-(1,3,4-thiadiazolyl), 2-benzothioazolyl, 2-benzoxazolyl, 2-benzoimidazolyl, 2-benzoselenazolyl, 2-quinolyl, 2-oxazolyl, 2-thiazolyl, 2-selenazolyl, 5-tetrazolyl, 2-(1,3,4-oxadiazolyl), and 2-imidazolyl.
R1 is preferably a 1- to 22-carbon aliphatic group, and more preferably, a 1- to 16-carbon aliphatic group.
R2 represents a substituent, and n represents an integer of 0 to 5. If n represents an integer of 2 or more, these R2""s can be the same or different. Also, adjacent R2""s can form a ring.
Examples of a substituent represented by R2 or a substituent suited to the groups described above and groups explained below are a halogen atom (e.g., a fluorine atom, chlorine atom, bromine atom, and iodine atom), hydroxyl group, carboxyl group, sulfo group, cyano group, nitro group, alkyl group (e.g., methyl, ethyl, and hexyl), fluoroalkyl group (e.g., trifluoromethyl), aryl group (e.g., phenyl, tolyl, and naphthyl), heterocyclic group (e.g., a heterocyclic group described in the explanation of R1), alkoxy group (e.g., methoxy, ethoxy, and octyloxy), aryloxy group (e.g., phenoxy and naphthyloxy), alkylthio group (e.g., methylthio and butylthio), arylthio group (e.g., phenylthio), amino group (e.g., amino, N-methylamino, N,N-dimethylamino, and N-phenylamino), acyl group (e.g., acetyl, propionyl, and benzoyl), alkylsulfonyl or arylsulfonyl group (e.g., methylsulfonyl and phenylsulfonyl), acylamino group (e.g., acetylamino and benzoylamino), alkylsulfonylamino or arylsulfonylamino group (e.g., methanesulfonylamino and benzenesulfonylamino), carbamoyl group (e.g., carbamoyl, N-methylaminocarbonyl, N,N-dimethylaminocarbonyl, and N-phenylaminocarbonyl), sulfamoyl group (e.g., sulfamoyl, N-methylaminosulfonyl, N,N-dimethylaminosulfonyl, and N-phenylaminosulfonyl), alkoxycarbonyl group (e.g., methoxycarbonyl, ethoxycarbonyl, and octyloxycarbonyl), aryloxycarbonyl group (e.g., phenoxycarbonyl and naphthyloxycarbonyl), acyloxy group (e.g., acetyloxy and benzoyloxy), alkoxycarbonyloxy group (e.g., methoxycarbonyloxy and ethoxycarbonyloxy), aryloxycarbonyloxy group (e.g., phenoxycarbonyloxy), alkoxycarbonylamino group (e.g., methoxycarbonylamino and butoxycarbonylamino), aryloxycarbonylamino group (e.g., phenoxycarbonylamino), aminocarbonyloxy group (e.g., N-methylaminocarbonyloxy and N-phenylaminocarbonyloxy), and aminocarbonylamino group (e.g., N-methylaminocarbonylamino and N-phenylaminocarbonylamino).
n is preferably 1 or 2, and more preferably, 1. R2 is preferably a group represented by R3 (to be described later).
X represents a hydrogen atom, halogen atom (e.g., a fluorine atom, chlorine atom, bromine atom, or iodine atom), R11xe2x80x94, R11Oxe2x80x94, R11Sxe2x80x94, R11OCOOxe2x80x94, R12COOxe2x80x94, R12(R13)NCOOxe2x80x94, R12CON(R13)xe2x80x94, xe2x80x94NO, xe2x80x94NO2, or xe2x80x94Nxe2x95x90Nxe2x80x94R11, and Y represents an oxygen atom or sulfur atom. R11 represents an aliphatic group, aryl group, or heterocyclic group, and each of R12 and R13 independently represents a hydrogen atom, aliphatic group, aryl group, or heterocyclic group. An aliphatic group, aryl group, and heterocyclic group represented by R11, R12, and R13 have the same meanings as R1.
Preferably, X represents a hydrogen atom, aliphatic group, aliphatic oxy group, aliphatic thio group, or R12CON(R13)xe2x80x94, and Y represents an oxygen atom. More preferably, X represents a hydrogen atom.
A compound represented by formula (I) of the present invention can be preferably represented by formula (II) below, and more preferably represented by formula (III) below: 
wherein R3 represents a hydrogen atom, halogen atom (e.g., a fluorine atom, chlorine atom, bromine atom, or iodine atom), cyano group, R12(R13)NCOxe2x80x94, or R12CON(R13)xe2x80x94, R4 represents a hydrogen atom or a group having the same meaning as R1, R5 represents an aliphatic group having 1 to 32, preferably, 1 to 22, and more preferably, 1 to 18 carbon atoms, m represents an integer of 0 to 4, and R1, R2, A, R12, and R13 represent groups having the same meanings as above.
Practical examples of a compound of the present invention will be presented below, but the present invention is not limited to these examples. 
A general synthesis method of a compound of the present invention will be described below.
An acid precursor of the present invention can be readily synthesized by route 1 or route 2 below: 
Explanation of Route 1
A compound represented by formula (I) can be synthesized by reacting compounds (a) and (b) (Z represents A, a halogen atom, phenoxy group, or p-nitrophenoxy group, preferably a halogen atom or p-nitrophenoxy group, and more preferably, a chloro atom).
A solvent for the reaction of (a) with (b) is preferably dichloromethane, chloroform, toluene, xylene, hexane, heptane, ethyl acetate, tetrahydrofuran, diethyl ether, acetonitrile, N,N-dimethylacetamide, or N,N-dimethylformamide, and more preferably, dichloromethane, toluene, ethyl acetate, or tetrahydrofuran.
The solvent amount is preferably 1 to 100 times (weight ratio), and more preferably, 3 to 20 times the amount of the compound (a).
Although the reaction of (a) with (b) can be performed with no base, it is preferably performed in the presence of a base. The base for use in the reaction of (a) with (b) is preferably pyridine, xcex1-, xcex2-, or xcex3-picoline, lutidine, N-methylmorpholine, N,N-dimethylaniline, N,N-diethylaniline, quinoline, sodium bicarbonate, sodium carbonate, potassium bicarbonate, or potassium carbonate, and more preferably, N,N-dimethylaniline, N,N-diethylaniline, or quinoline.
In the reaction of (a) with (b), the reaction temperature is preferably xe2x88x9220xc2x0 C. to 100xc2x0 C., and more preferably, 0xc2x0 C. to 50xc2x0 C.
In the reaction of (a) with (b), the reaction time is preferably 5 min to 5 hr, and more preferably, 30 min to 2 hr.
The compound (a) can be readily synthesized by the reaction of a corresponding 5-amino-1-naphthol derivative and R1-Hal. (Hal. represents a halogen atom, preferably a bromine atom or iodine atom). The compound (b) can be easily synthesized by the reaction of AH with phosgene, thiophosgene, trichloromethylchloroformate, bis(trichloromethyl) carbonate, phenyl chlorocarbonate, or p-nitrophenyl chlorocarbonate.
The amount of (b) is preferably 0.5 to 2 equivalent times, and more preferably, 0.8 to 1.2 equivalent times the amount of (a). When a base is used, the amount of the base is preferably 0.5 to 10 equivalent times, more preferably, 0.8 to 5 equivalent times, and most preferably, 0.9 to 2 equivalent times the amount of (a).
Explanation of Route 2
A compound represented by formula (I) can be synthesized by once converting the compound (a) into a compound (c) (Hal. represents a halogen atom, preferably a chlorine atom) and reacting this compound (c) with the compound AH.
As a reagent for converting (a) into (c), it is possible to use, e.g., phosgene, thiophosgene, trichloromethylchloroformate, or bis(trichloromethyl) carbonate.
A solvent for the reaction of converting (a) into (c) is preferably dichloromethane, chloroform, toluene, xylene, hexane, heptane, ethyl acetate, tetrahydrofuran, or diethyl ether, and more preferably, dichloromethane, toluene, ethyl acetate, or tetrahydrofuran.
The solvent amount is preferably 1 to 100 times (weight ratio), and more preferably, 3 to 20 times the amount of the compound (a).
The reaction of converting (a) into (c) can be performed with no base or in the presence of a base. The base for use in the reaction of converting (a) into (c) is preferably pyridine, xcex1-, xcex2-, or xcex3-picoline, lutidine, N-methylmorpholine, N,N-dimethylaniline, N,N-diethylaniline, or quinoline, and more preferably, N,N-dimethylaniline, N,N-diethylaniline, or quinoline.
In the reaction of converting (a) into (c), the reaction temperature is preferably xe2x88x9220xc2x0 C. to 100xc2x0 C., and more preferably, 0xc2x0 C. to 50xc2x0 C.
In the reaction of converting (a) into (c), the reaction time is preferably 5 min to 5 hr, and more preferably, 30 min to 2 hr.
The amount of the reagent for converting (a) into (c) is preferably 0.5 to 2 equivalent times, and more preferably, 0.8 to 1.2 equivalent times the amount of (a).
A solvent for the reaction of (c) with AH is preferably dichloromethane, chloroform, toluene, xylene, chlorobenzene, hexane, heptane, ethyl acetate, tetrahydrofuran, diethyl ether, acetonitrile, N,N-dimethylacetamide, or N,N-dimethylformamide, and more preferably, dichloromethane, toluene, xylene, chlorobenzene, ethyl acetate, or tetrahydrofuran.
The solvent amount is preferably 1 to 100 times (weight ratio), and more preferably, 3 to 20 times the amount of the compound (c).
The reaction of (c) with AH can be performed with no base or in the presence of a base. The base for use in the reaction of (c) with AH is preferably triethylamine, diisopropylethylamine, sodium methoxide, sodium t-butoxide, potassium t-butoxide, sodium hydride, pyridine, xcex1-, xcex2-, or xcex3-picoline, lutidine, N-methylmorpholine, N,N-dimethylaniline, N,N-diethylaniline, quinoline, sodium bicarbonate, sodium carbonate, potassium bicarbonate, or potassium carbonate, and more preferably, triethylamine, diisopropylethylamine, sodium methoxide, sodium t-butoxide, potassium t-butoxide, sodium hydride, pyridine, xcex1-, xcex2-, or xcex3-picoline, or lutidine.
In the reaction of (c) with AH, the reaction temperature is preferably xe2x88x9220xc2x0 C. to 170xc2x0 C., more preferably, 0xc2x0 C. to 150xc2x0 C., and much more preferably, 20xc2x0 C. to 120xc2x0 C.
The amount of AH is preferably 0.5 to 10 equivalent times, more preferably, 0.8 to 5 equivalent times, and much more preferably 0.9 to 2 equivalent times the amount of (c). The amount of the base is preferably 0.5 to 2 equivalent times, and more preferably, 0.8 to 1.2 equivalent times the amount of AH.
In the reaction of (c) with AH, the reaction time is preferably 5 min to 10 hr, and more preferably, 30 min to 5 hr.
A method of regenerating a compound (AH) having an acidic proton from a compound of the present invention will be described below.
As indicated by a formula presented below, a 1-naphthol derivative of the present invention can rapidly release Axe2x88x92 (or AH) along with an intramolecular ring closure reaction when a nucleophilic substituent is introduced to its 4-position by some method. The nucleophilic substituent is preferably xe2x80x94NHR6 (R6 represents a hydrogen atom or a group having the same meaning as R1 described previously), xe2x80x94OH, or xe2x80x94SH, and more preferably, xe2x80x94NHR6 or xe2x80x94OH. 
The following methods are possible as a method of introducing the nucleophilic substituent, but the present invention is not limited to these methods.
(1) If X represents xe2x80x94NO, xe2x80x94NO2, or xe2x80x94Nxe2x95x90Nxe2x80x94R11 in formula (I), they can be converted into xe2x80x94NH2 by a general reducing reaction (e.g., a method described in xe2x80x9cNew Experimental Chemistry Course 14xe2x80x9d, Maruzen K. K., pp. 1332-1336). 
(2) If X represents R11Oxe2x80x94, R11OCOOxe2x80x94, R12COOxe2x80x94, or R12(R13)NCOOxe2x80x94 in formula (I), the R11xe2x80x94O bond can be cut by using a Lewis acid such as aluminum chloride or boron tribromide or can be converted into xe2x80x94OH by performing decarbonylation by hydrolysis. 
(3) Regardless of X in formula (I), an amino group can be introduced by reaction with the oxidized form of a developing agent used in a silver halide photosensitive material (e.g., phenylenediamine-based and aminophenol-based developing agents described in U.S. Pat. Nos. 2,193,015, 2,592,364, and 5,240,821 and Jpn. Pat. Appln. KOKAI Publication No. 48-64933, sulfonylhydrazine-based developing agents described in European Patent Nos. 545491A1 and 565165A1, carbamoylhydrazine-based developing agents described in Jpn. Pat. Appln. KOKAI Publication Nos. 8-286340, 9-152702, and 9-211818, and 4-aminoantipyrine; preferably, p-phenylenediamine-based developing agents such as 4-amino-N,N-diethylaniline, 3-methyl-4-amino-N,N-diethylaniline, 4-amino-N-ethyl-N-xcex2-hydroxyethylaniline, 3-methyl-4-amino-N-ethyl-N-xcex2-hydroxyethylaniline, 3-methyl-4-amino-N-ethyl-N-xcex2-methanesulfonamidoethylaniline, and 3-methyl-4-amino-N-ethyl-N-xcex2-methoxyethylaniline). The following formula indicates an example in which an arylamino group is introduced to the 4-position of naphthol by the reaction of a compound represented by formula (I) with a p-phenylenediamine-based developing agent in the oxidized form (each of R31, R32, and R33 independently represents an aliphatic group). 
(4) If X is a hydrogen atom in formula (I), a hydroxyl group can be introduced by an oxidation reaction (e.g., a method described in xe2x80x9cNew Experimental Chemistry Course 15xe2x80x9d, Maruzen K. K., pp. 638-645, or a reaction using an enzyme in a living body). If X is a hydrogen atom, an amino group can be introduced by once introducing a nitro group, nitroso group, or azo group to the 4-position and reducing the compound by the method explained in item (1) above.